["International Journal of Finance &Economics, EarlyView. ", "\nABSTRACT\nThis paper examines the relationship between spatial marginal expansion and financing constraints among small and medium enterprises (SMEs) using a machine learning approach. Based on panel data from China's A‐share listed companies (2008–2023), we identify an inverted U‐shaped relationship. Spatial expansion influences financing constraints through channels such as firm size, commercial credit, and equity structure. Further analysis reveals a positive correlation between SME financing constraints and regional market development. Thus, accelerating the formation of a unified national market requires greater emphasis on SMEs as key connectors in cross‐regional production and trade. Breaking regional protectionism and market segmentation can help optimize the spatial allocation of productive forces and expand financing opportunities. These findings offer insights for corporate debt financing strategies.\n"]